A huge realization came to me recently, as I immersed myself in books and old movies about the US Civil War. We all know that the Confederate nation that lost this bitter war was also soundly trounced by the judgement of history, since the Confederacy’s key pro-slavery position is clearly on its wrong side.

But the 150 years that have passed since the end of the Southern rebellion might have put a thick patina on the moral arguments that once energized the rebellion, and I made it my goal during my recent bout of Civil War reading to try to understand how a typical well-educated and high-principled Southerner would have explained the Southern position. There were, of course, many thoughtful intellectuals in the Civil War South, and we can take two of the four main characters in Margaret Mitchell’s novel Gone With The Wind as useful examples. The noble Ashley Wilkes is a brave Confederate officer who loves books, who loses himself in his vast library, who befuddles Scarlett O’Hara with talk of the Gotterdammerung. His equally noble wife Melanie Hamilton Wilkes relishes the opportunity to discuss literature and morality; we first meet her condemning the British novelist William Makepeace Thackeray for being “a cynic” and “not the gentleman Dickens is”.

As a lifelong American Northener, I grew up with a shallow perception of Confederate politics as essentially unprincipled. It’s clear today that the Confederate position on slavery was terribly wrong — but even so, an ethical philosopher who wishes to understand history can’t stop there. There’s a puzzle to be solved, because even though we see the Confederate position to be wrong today, we must recognize that the Confederacy was populated with principled intellectuals who somehow convinced themselves that it was right. How, exactly, did they convince themselves of this, and what can we learn about our own closely held beliefs from their example?

There is a great contradiction in the high moral self-regard of any evil society, and every great contradiction reveals a broad chasm that can be rewardingly explored. I took a stab in this direction a year ago when I blogged about the widely celebrated South Carolina politician and one-time Vice-President John Calhoun, who argued that Southern society was kind and generous to its African slave population, and that the institution of slavery represented a harmonious natural arrangement less inhumane than, say, the ghastly child-labor factories of England. Calhoun’s position feels very weak today — but there can be little doubt that the many real-life equivalents of Ashley and Melanie Wilkes would have believed it with all their hearts.

Likewise, while it’s nearly horrifying to say this today, there can be little doubt that German intellectuals who supported the Nazi Party before and during World War II sincerely believed that they were on the correct side of moral law, that the rampaging mobs of young Chinese Maoists who terrorized their elders during Mao’s Cultural Revolution believed this about themselves too, that even the brutal machete-wielding Hutus in Rwanda in 1994 must have believed this as they murdered Tutsi men, women and children on the streets and in the homes and shops and churches where they had previously lived together in peace and friendship. Certainly the many fans of Osama bin Laden believed they were cheering for the good side when they cheered his success on September 11, 2001.

We cannot flatter ourselves that these partisans of the past were stupider than we are today, or less honest about themselves than we are. If we wish to do the dirty work of ethical philosophy, we must try to understand their points of view as they understood them. We must credit these bygone intellectuals with high ideals, and study how these high ideals crashed. Only by doing this exercise can we ensure that we understand our own high ideals.

The fact that these evildoers regarded themselves as highly moral seems impossible, and yet the evidence can be found in all the above cases to prove it true. A quick look at familiar historical examples points to the statement of a basic principle that can be used as a useful tool for ethical inquiry, and a basic building-block for the deep study of history. The principle is this:

While a society or civilization may be effectively evil, no society or civilization can be or ever has been knowingly evil. A society always believes itself to be morally strong, and will always convince itself of its moral strength through published writings and public discourse.

Because I’m a good empiricist, I would never bother proposing this principle on theoretical grounds. I propose it instead on the basis of available evidence: the published writings and public discourse every “evil” civilization in history has left behind. We can all name nations or civilizations that have committed evil acts, but can you name a single nation or civilization in history that has not left behind a body of published words — newspaper and magazine articles, books, public speeces — vigorously pronouncing its moral goodness? I don’t think you can.

It’s a notable fact that even the many totalitarian governments that have been hostile to free speech and free publication of newspapers, magazines and books (like Hitler’s Germany or Stalin’s Soviet Union) successfully used speeches, newspapers, magazines, books to proclaim their moral positions and principles.

This proposed universal truth that every society regards itself as moral may seem like a mild invention, but it’s not. It’s a powerful tool, especially if we learn how to apply it intelligently to our study of the past. It means we can use examples from history to observe how sincere ideals can be subverted into evil results.

The discovery here is that the evidence of any past society’s self-regard is definitively more transparent, available and searchable by historians, philosophers and researchers than the evidence of any individual person’s self-regard can be. We cannot study Hitler or Stalin or Mao’s private thoughts, because private thoughts do not leave a paper trail. But every society and civilization, no matter how oppressive, does leave a paper trail.

We don’t know if Chairman Mao sincerely believed himself to be upholding high moral standards during his murderous decades of leadership, but we can determine with absolute certainty that the shared public mind of Mao’s China believed itself to be upholding high moral standards, since the archives of public discourse during the Mao era are there for us to read.

Of course, the recorded public discourse of Mao-era China is a corrupt text, a product of extreme and violent censorship. However, speech doesn’t have to be free to carry historical meaning. Every society has recorded its “official” self-justification, and it sometimes seems that the most murderous and oppressive societies wrote even more texts than the others. These texts lay out the public justifications for history’s worst atrocities, as they were understood by the perpetuators themselves in Mao’s China, in the Slave Trade, in Nazi Germany and Hutu Rwanda and Pakistan.

If we wish to discover new insights into the puzzles of human history, and if we wish to critically examine our own deepest beliefs to make sure we are not overly complacent in declaring ourselves to be thoroughly morally “good”, it seems to me that the vigorous application of the principle stated here — we can call it the Ashley Wilkes Principle, I suppose — will be a very useful tool. We may discover surprising things about societies of the past. We may even discover surprising things about ourselves.